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Active and Passive Electronic Components
Volume 2008 (2008), Article ID 356049, 6 pages
Research Article

Compact Bandstop Filters with Extended Upper Passbands

Advanced Technologies Research Center (ATRC), Department of Electrical Engineering, King Saud University, P. O. Box 800, Riyadh 11421, Kingdom of Saudi Arabia

Received 12 March 2008; Revised 17 May 2008; Accepted 2 June 2008

Academic Editor: Yalin Lu

Copyright © 2008 Majeed A. S. Alkanhal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper presents new compact bandstop filters (BSFs) with extended upper passbands. In the basic proposed filter configuration, the conventional quarter-wavelength open-stub resonators are replaced with equivalent two-section stepped impedance resonators. Transmission line analysis is used to determine the dimensions of the equivalent stepped impedance sections. The filter structure is analyzed using a full wave electromagnetic (EM) simulator and then realized at 2.3 GHz band. Experiments have also been done to validate the performance of the design concept. Compared with the conventional quarter-wavelength-based bandstop filter, significant extensions of the upper passband beyond 9 GHz and 40% size reduction are achieved. Two other variations of the proposed basic BSF with further size reduction (more than 60%) are implemented and their measured performances are verified.